Pulse length measurement



July 18, 1950 J. P. sH 2,515,968

PULSE LENGTH MEASUREMENT Filed May 7, 1947 JOHN P. SHANKLIN PatentedJuly 18, 1950 PULSE LENGTH MEASUREMENT John P. Shanlrlin, Baltimore, Md,assignor to Bendix Aviation Corporation, Towson, Md., a

corporation of Delaware Application May 7, 1947, Serial No. 246,605

Claims. 1

This inventi n i di e ed o elect ca r ays- More specifically it isdirected to relays respondin; only o pu ses o ele tr al e gy avi g apreselected width or dur tion.

In s l ctive a ling sy ms, wher in t s sired to ener ize o e of a p uraity of cir uits f m. a rem point over a s gle ommun ation channel s veraar an ement e nown- In one of these sys ems. eq ncy sele e tors at thereceiving terminal actuate the circuit corr spond n to the req en y o thei e energy. Another general class of selective calling sys em is thatuse in the d a l p e y t whe ei th ansmitter prod ce a r s o shortelectrical ulse an a s eppi g ci cuit at the rec iv end ounts t pulses,a d eo uet s the circui co responding to the .nnmh ro pu received.

It is an object of this invention to proyide a sele tive ca in sys m whein le on is made n the as s o puls duration rathe han pu se count as inhe teleph ne sy tem It will h ma if t th t the n tant nven ion may he neither to multiply the number of channels available in either therequency e c e o he countin syste s, or al n as a s p e p lyha nel arragem nt.

This object is a aine by h use of e plura ty of relay and tim elaycircuit h re n a first relay is en r ze when it ceives a p se hay reateu a ion tha a red er in d minimum, and a seco d re ay prevents the fir fom operating if the pulse has greater duration than a p e t min dmaximum- Other and further objects and advanta es will more fully appearfrom the following detailed .description when the same i read inconnection with the accompanying drawing wherein there is illustrated apulse-duration selective relay systern in accordance with the instantinvention.

Referring now to the accompanying drawing,

nal of a battery 16. The remaining terminal .of

the batte y t is conn cted throug a orma y closed switch it! and hrou ha pair o n rmallyclosed contacts on a relay contact assembly It; to thejunction of the resistor ii and the coil I: ,3 second set of contacts.no mally-op n. on the assembly i8 is arranged to close a circuitshorting the coil l2 when the coil l9 associated therewith energized.One terminal of the coil i9 is com nected to ground, and the otherterminal is connected to the input terminal Hi through a re sistor 21!.A condenser 2| is connected in shunt with the coil iii. The junction ofthe resistor H and the coil 12 is connected to ground through a seriescircuit comprising a resistor 22 and a relay coil 23, and a condenser 24is connected between the junction of the resistor 22 and the coil 23 andground. A set of switch contacts 25 is associated with the relay coil23, and may b neoted as control terminals to an external circuit.

In operation signal pulses of various durations, but having constantamplitude, are applied to the input terminals l0, M. The resistor H andthe condenser is form a delay circuit so that input signals will notenergize the coil l2 sufficiently to close the contacts I5 unless theyexceed a minimum duration 231 which, by way of example, can be taken astwo seconds. Similarly the re sistor 20 and the condenser 21 form asecond delay circuit so that input signals will not energize the coil E9sufficiently to operate the contact assembly 18 unless they exceed asecond, greater, duration i2 such as three seconds. The coil 23 isconnected in shunt with the coil l2 through delay network comprising theresistor 22 and the condenser 24, so that the contacts 25 will not beenergized unless energizing current passes through the coil I2 for athird minimum .dura tion is which, can be taken as four seconds.

If a pulse having a duration less than t1, 252, or ii is applied to theinput terminals it can be seen that none of the relays will operate, andthe entire circuit will remain in a lie-energized state.

If a pulse having a duration greater than 161, but less than t2 or is isapplied to the input terminals it can be seen that the contacts 15 willclose, and current from the battery 1-5 will flow through the switchassembly l8 and will hold the coil 12 in an energized conditionregardless of the eventual cessation of the pulse. After the batterycurrent has energized the coil for a time ti such that t1+t4=t3, thecoil 23 will operate the switch 25, and the external circuit will beactuated. The battery will hold the coils l2 and 23 in an energized tateuntil the switch H is manually opened to reset the system. The coil :9is energized from the battery when the system is in the locked-on state,but insuflicient current flows through the coil 19 to actuate thecontact assembly l8 because of the voltage drop through the resi ors Han 20 whi h included in the series circuit. Relay coil 23 cannot beoperated solely by a signal pulse of a duration less than Ta because ofthe long time constant of the circuit comprising the components II, 13,22 and 24. Pulses of sufilcient duration to cause coil l9 to operateswitch [8 do not reach coil 23, which is short circuited by operation ofthe switch.

If a pulse having a duration greater than t2 is applied to the inputterminals, the switch contacts l are closed at time h, as before, butthe coil I9 is energized sufficiently at time t2 to operate the switchassembly l8, to de-energize the coil l2. This action takes place beforethe coil 23 has become suificiently energized, and no effeet i producedin the external circuit.

Thus, by proper choice of the various time constants it can be seen thatthe above-described circuit will select pulses having a duration betweenpredetermined limits, and will be unaffected by signals not included inthat range. Similar arrangements having difierent time constants may beconnected to the same set of input terminals so that a plurality ofoutput circuits may be controlled from a single communications circuit.

The use of electron tubes at one or more points in the circuit toincrease the efiicacy of the system may be advisable if greatestaccuracy is to be attained. Inasmuch as relays are shown for purpose ofillustration only, vacuum tube, or thyratron circuits may be usedwithout departing from the scope and spirit of the invention.

What is claimed is:

1. In a pulse-responsive electrical relay system: a first relay having afirst time constant circuit operatively associated with the energizingcoil thereof; a second relay having a second time constant circuitoperatively associated with the energizing coil thereof; a third relayhaving a third time constant circuit operatively associated with theenergizing coil thereof; a source of pulse signals of differingdurations; and a source of relatively constant voltage; circuitconnections from said source of pulse signals through said first timeconstant circuit to said first relay coil; circuit connections from saidsource of pulse signals through said second time constant circuit tosaid second relay coil; whereby said first relay is momentarily actuatedby pulse signals having a duration greater than a preselected minimum,and said second relay is momentarily actuated by pulse signals having aduration greater than a preselected maximum; switch means associatedwith said first relay whereby a holding current derived from said sourceof constant voltage is applied to the said first relay coil during theinterval between the actuation of said first and second relays; switchmeans operated by the actuation of said second relay to disconnect saidsource of constant voltage from said system; and circuit connectionsbetween said first relay coil and said third relay coil including saidthird time constant circuit applying current from said source ofconstant voltage to said third relay whereby said third relay isactuated if said first relay coil is ener gized by said holding currentfor a period of time greater than a second preselected minimum.

2. In a pulse-responsive electrical relay system: a first relay having afirst time constant circuit operatively associated with the energizingcoil thereof; a second relay having a second time constant circuitoperatively associated with the energizing coil thereof; a third relayhaving a third time constant circuit operatively associated with theenergizing coil thereof; a source of pulse signal of differingdurations; and a source of relatively constant voltage; circuitconnections from said source of pulse signals through said first timeconstant circuit to said first relay coil; circuit connections from saidsource of pulse signals through said second time constant circuit tosaid second relay coil; wherei by said first relay is momentarilyactuated by pulse signals having a duration greater than a preselectedminimum, and said second relay is momentarily actuated by pulse signalshaving a duration greater than a preselected maximum; switch meansassociated with said first relay whereby a holding current derived fromsaid source of constant voltage is applied to the said first relay coilduring the interval between the actuation of said first and secondrelays; switch means operated by the'actuation of said second relay todisconnect said source of constant voltage from said'system'; andcircuit connections between said first relay coil and said third relaycoil including said third 'time'constant circuit applying current fromsaid source of constant voltage to said third relay whereby said thirdrelay is actuated if said first relay coil is energized by said holdingcurrent for a period of time greater than a second preselected minimum;and a switch associated with said source of constant voltage whereby thesaid holding current may be manually interrupted.

3. In a pulse-responsive switching system: a first electrically actuatedswitch having a first control circuit and a first time constant circuitassociated with said control circuit; a second electrically actuatedswitch having a second control circuit and a second time constantcircuit as-- sociated with said second control circuit; a thirdelectrically actuated switch having a third control circuit and a thirdtime constant circuit associated with said third control circuit; asource of pulses of electrical energy, said pulses having differingdurations; a second source of electrical energy having a substantiallyconstant average amplitude; circuit connections from said source ofpulses through said first time constant circult to said first controlcircuit; circuit connections from said source of pulses through saidsecond time constant circuit to said secondcontrol circuit; the timeconstants of said first and second time constant circuits being soselected that said first switch is momentarily actuated by pulses havinga duration greater than a preselected minimum, and said second switch ismomentarily actuated by pulses having a duration greater than apreselected maximum; circuit connections including said first and secondswitches whereby a holding current derived from said second source isapplied to said first control circuit during the interval'between theactuation of said first and'second switches; circuit connectionsincluding said third time constant circuit between said firstand thirdcontrol circuits applying current from said second source of energy tosaid third control circuit when said holding current is applied to saidfirst control circuit, the time constant of said third time constantcircuit being so selected that said third switch is actuated if saidfirst switch is ener gized by said holding current for a period of timegreater than a preselected minimum.

4. In a pulse-responsive switching system: a first electrically actuatedswitch having a first control circuit and a first time constant circuitassociated with said control circuit; a second electrically actuatedswitch having a second control circuit and a second time constantcircuit associated with said second control circuit; a thirdelectrically actuated switch having a third control circuit and a thirdtime constant circuit associated with said third control circuit; asource of pulses of electrical energy, said pulses having differingdurations; a second source of electrical energy having a substantiallyconstant average amplitude; circuit connections from said source ofpulses through said first time constant circuit to said first controlcircuit; circuit connections from said source of pulses through saidsecond time constant circuit to said second control circuit; the timeconstants of said first and second time constant circuits being soselected that said first switch is momentarily actuated by pulses havinga duration greater than a preselected minimum, and said second switch ismomentarily actuated by pulses having a duration greater than apreselected maximum; circuit connections including said first and secondswitches whereby a holding current derived from said second source isapplied to said first control circuit during the interval between theactuation of said first and second switches; circuit connectionsincluding said third time constant circuit between said first and thirdcontrol circuit applying current from said second source of energy tosaid third control circuit when said holding current is applied to saidfirst control circuit, the time constant of said third time constantcircuit being so selected that said third switch is actuated if saidfirst switch is energized by aid holding current for a period of timegreater than a preselected minimum; and a fourth switch associated withsaid second source whereby said holding current may be interrupted.

5. A pulse responsive electrical relay system comprising a first, asecond and a third relay, a respective time constant circuit associatedwith each of said relays, a source of pulse signals, means applyingsignals from said source to said relays by way of said time constantcircuits, a source of constant voltage, a switch operable by said firstrelay to connect said source to said system in a manner to supplyholding current to said first relay and to supply current to said thirdrelay by way of its time constant circuit, a switch operable by saidsecond relay to disconnect said source of constant voltage from saidsystem, the time constants of said respective time constant circuitsbeing so selected that said first relay is operated in response to apulse of a selected minimum duration, said second relay is operated inresponse to a pulse of a selected duration reater than said minimumduration and said third relay is operated in response to a pulse of saidminimum duration plus the application thereto of current from saidsecond source, for a total time which exceeds the response time of saidsecond relay.

JOHN P. SHANKLIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,968,078 Hershey July 31, 19342,094,733 Byrnes Oct. 5, 193'? 2,389,078 Perry Nov. 13, 1945

